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Treatment of wastewater from textile whitening with a coagulant based on Moringa Oleifera
Optical Brighteners (OB) are a type of dyes that can be found in textile whitening wastewater. This OB are poorly biodegradable and colourless. OB can’t be seen with a naked eye; nevertheless, they emit fluorescence when are exposed to ultraviolet light. OB are emerging organic pollutants. OBs can only be partially adsorbed by sludge in biological systems, therefore OBs can reach the environment. Besides OBs, textile wastewaters from whitening process used to have recalcitrant compounds, oxidizing agents, high salinity and high alkalinity. On the other hand, Moringa Oleifera can be used as natural coagulant in alkaline waters. Moringa Oleifera seeds contain high levels of water-soluble proteins with coagulating properties. Also, Moringa Oleifera seeds contain around 30% of oil that has an important commercial value. The waste cake from Moringa Oleifera oil extraction can be recovered and it can be used as a coagulant. In this work, we assessed the removal of a OB from wastewater with a coagulant solution of Moringa Oleifera. We used the “Fluorescent Brightener 134” (OB-134), a diaminostilbenedisulphonic acid derivate. We tested OB 134 solutions at different concentrations (100, 450 and 1000 mg/L). Moringa coagulant solutions (5 and 10 % w/v) were made from moringa seeds milled and degreased. Before test OB solutions pH was adjusted to 10, then flocculation tests (Jar-test) were carried out with moringa coagulant. Different ratios of [moringa coagulant concentration]:[OB concentration] from 1:1 to 7:1 were tested. Also, OB solutions different pH were tested (from 5 to 11). We analysed the OB-134 concentration in water whereby UV-VIS spectrophotometer. Moringa Oleifera coagulant eliminated up to 90% of OB of simulated wastewaters and it was not affected by the pH variations. In addition, we studied the removal of the OB on wastewater from optical-chemical whitening process. We simplified and reproduced an optical-chemical whitening recipe process in laboratory. We used the dying method “all in” at liquor ratio 1/10 (fibre weight/water volume). In this optical-chemical process, we used fibber 100% cotton, OB-134 as optical whitener and H2O2 at 50% as oxidant. Initial OB-154 concentration was 1000 mg/L. We tested moringa coagulant before and after optical-chemical whitening. Before the whitening process, moringa coagulant removed up to 90% OB-134; we concluded that the presence of oxidizing substances did not affect the effectiveness of the moringa coagulant. After the whitening process, we recovery the wastewater of this optical-chemical process; the concentration of OB-134 in wastewater was around the half than initial concentration (450 mg/L). We studied the removal of OB-134 with Moringa Oleifera from wastewater of the optical-chemical whitening. The moringa coagulant removed up to 60% of OB; anyway, the final concentration of OB-134 after moringa treatment was 80% lower than initial concentration (< 200 mg/L). This study shows that the textile whitening wastewater can be treated successfully with this natural coagulant. Also, it is possible to recover the supernatant and reused it in new textile processes, reusing both the water and residual reagents. This would minimize the expenses and the water footprint of this textile process.